The present invention relates to a slave station, a master station, a bus system and a method of operating a bus system. Conventional bus systems where a plurality of slave stations are connected to a master station by bus lines. Electric power is supplied to the slave stations by the power supply voltage supplied by the master station.
The slave station of the present invention has the advantage, however, that not all slave stations are connected to the power supply voltage at the same time. Therefore, the bus system is initialized for each slave station individually in succession, so that the bus lines are not carrying high loads. In addition, each slave station can thus be initialized independently of the other slave stations, so that any faults occurring can be allocated to the individual bus stations especially easily. It is thus recognized quickly and easily during initialization whether the bus system is fully functional and where faults are when they occur. The master stations of the present invention have the advantage that with a ring structure, faults can be compensated especially well, because the individual slave stations can be reached by different pathways. An especially simple means for detecting faults consists of current monitoring in the master station, in particular when the bus stations are initialized individually and in succession. The method of the present invention is suitable in particular for detecting a fault in the bus system and guaranteeing at least the functioning of the remaining system through suitable measures.
Due to the use of a test switch with a limited current flow, the lines downstream from the slave station and/or the downstream slave stations can be tested for a short circuit. A working energy storage mechanism which can also be charged over the bus lines may be provided for storing large quantities of energy. The ongoing energy for operation of the slave station is also obtained from the electric voltages on the bus lines. The slave stations can be driven to trigger predetermined actions in accordance with messages sent over the bus lines. In addition, the master station can send messages causing a reconfiguration of the slave stations. To do so, first the connecting switches are opened again. During initialization, the individual addresses can also be issued by the master station. The logic required for this can be minimized in particular because only one individual slave station is initialized in each case. During or after the initialization, the slave stations can send return signals back to the master station to thereby confirm their functionality. With a ring structure, messages can be supplied to both sides of the ring. Individual slave stations are still achieved even when there is a disturbance between two stations or in one slave station. Analysis of the current flow in operation of the bus system can give an indication of a possible disturbance.